Flue gas desulfurization processes applied to fuels containing high chloride concentrations utilize by-product gypsum from the process stream.
One such process for making by-product gypsum is disclosed in U.S. Pat. No. 4,136,998 Bassier et al.
The utilization of a by-product gypsum process results in a calcium chloride buildup in the Fuel Gas Desulfurization system from fuels or water resource containing significant chlorides which interferes with the absorption and utilization of the lime or limestone reagent. Process systems proposed for such conditions result in a generation of solutions and slurries of calcium chloride. Although these materials can be processed into concentrated brines they still constitute a problem in handling and ultimate disposal. One method for converting the calcium chloride brine to a less difficult to handle material is to dry calcium chloride at elevated temperatures to form either the monohydrate or anhydrous calcium chloride. In either the monohydrate or anhydrous form, the calcium chloride handles much better in conventional conveying equipment.
Calcium chloride-dihydrate to hexahydrate are deliquescent in property. These forms of calcium chloride, when exposed to the atmosphere absorb water on the solid surfaces. The resulting surface moisture content influences the physical properties such that partial agglomeration and surface liquefaction occurs. The anhydrous and monohydrate forms are much lower in deliquescent tendencies and maintain the particle free flow much better in conventional solids. But, drying operations to form anhydrous and monohydrates are costly and energy consuming.